A crankshaft, which is a component of an engine, includes journal sections, crank pins, and webs each for coupling the journal section and the crank pin to each other. When the crankshaft is delivered, a quality inspection (ultrasonic examination) is required for these sections. The quality inspection is generally carried out through manual scanning of probes. However, the manual inspection takes a very much time, and thus requires many man-hours for a large crankshaft having a large diameter or many numbers of pins.
On the other hand, a system for automating a quality inspection for a cylindrical shaft used for turbine and the like without the crank pin sections (eccentric sections) is known as disclosed in Patent Literature 1. This system is a system in which a probe is brought in contact with a surface of the shaft, and peripheral scanning for flaw detection is carried out while the shaft is being rotated. The surface flaw detection for the journal section can be automatically carried out by rotating the crankshaft in this system. However, the surface flaw detection cannot be carried out on the crank pin which revolves eccentrically in this system. In other words, the crank pin cannot be rotated about the axial center of the crank pin, and the system cannot be applied to scanning for the flaw detection other than that for the journal sections.